ipv6: move tcpv6_protocol and udpv6_protocol to net_hotdata

These structures are read in rx path, move them to net_hotdata
for better cache locality.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240306160031.874438-13-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>